Laminated sheet heat-sealable container



Nov. ll, 1947. R. A. FARRELL Erm.

LAMINATED SHEETv HEAT-SEALABLE.' CONTAINER Filed Jan. 22. 1944 2Sheets-Sheet 1 L k/yner m diz@ Nov. 11, 1947. R. A. FARRELL Erm.2,430,459A

LMINATED SHEET HEAT-SEALBLE CONTAINER 'I Filed Jan. 22. 1944 2Sheets-Sheet 2 n"""` Wmv' 111111111111111 lilla/111 11,1111 l vated andbrought ?atented Nov. 1l, 1947 2,430,459 marmeren sneer naar-Smm commenRobert A. Farrell and Charley L. Wagner,

Menasha, Wis.,

assignors to Marathon Gomration, a corporation ot Wisconsin applicationJanuary 2z, 1944, serial Nq.

7 Claims. (Cl. 229-55) This invention relates to packages and containersformed from heat-scalable sheet materials'not havingany exposed coatingmaterial on its outer surfaces. More specically, this invention relatesto packages and containers made of heat-scalable sheet material having acomposition provided internally of the-sheet material that is notnormally exposed, but which is actito thesurface to provide an adhesivenlm which, forms a seal upon application of heat and pressure edareadesired to be sealed.

Further details and advantages of the invention will be apparent fromthe following specication and drawings wherein: v

Figure 1 is a perspective view of the heat-sealable sheet materialpartly broken away' to show the components thereof thatis used formaking packages and containers,

Figure 2 is an enlarged sectional view taken on lines 2-2 of Figure 1, l

Figure 3 is a plan view of a bag made of the heat-scalable sheetmaterial illustrated in Figure l,

Figure 4 is an enlarged fragmental sectional view taken on lines I-l ofFigure 3,

Figure 5 is an enlarged fragmental sectional view of the upper portionof Figure 4,

Figure 6 is an enlarged sectional view lines 6-6 of Figure 3, i

Figure 'l is a perspective view of a package wrapped and sealed in theheat-sealable sheet of Figure 1,

Figure 8 is an enlarged fragmental sectional view taken on lines B-S ofFigure '1,

Figure 9 is an enlarged fragmental sectional view of the seam portion A'shown in Figure 8,

Figure 10 is an enlarged fragmental sectional view taken on lineslt--ill oi Figure 7, and

Figure 11 is an enlarged fragmental sectional view of the seam portionB' shown in Figure 10.

Hitherto available heat-scalable sheet materials for packaging purposesand for making containers have been provided with a surface coat- ,ng ofsuitable compositions which are activated or softened by action of heatwhen a seal or seam is to be formed. Such sheet materials are dimcult tohandle prior to use due to their pressurev sensitive propertiesv whenthey are stacked or rolled up as the outer coating composition has atendency to cause blocking or sticking together of the contacting sheetsor layers. Furthermore, such prior external coatings cause difficultywhen the sheet materials are handled by wrapping machinery as thecoating may adhere to taken on to any suitably selectcause blocking orcause effectively overcome lize an efiicient heat-scalable sheet made ofsusheet 3, as shown in machine parts or scrape oi! and accumulate onmoving parts and thus prevent eiiicient operation. There are also manysticky and soft types of heat-scalable compositions that could not bepossibly used as external coatings that can now be used in heat-scalablesheets made in accordance with our invention as the composition in oursheet is not exposed and will not adhesion of any contacting materials.

These disadvantages and by our invention as we utiperposed' plies ofsheet materials `without having any esternal coating thereon of anykind. The sheets are united by an intermediate continuous nlm formed ofa A suitable ,thickness on "basis weight (pounds per 480 sheets size 24x 36 in.) so that upon application of heat and pressure to any selectedarea thereof an adhesive film will be generated on the outer surface ofone of the shee According to one embodiment of our invention we utilizea combined sheet material, comprising a base 1 and 2, and a-relativelyporous sheet material I, these sheets being united by an intermediatecontinuous flexible smooth uniform thermoplastic tllm 2 of a suitablecomposition. An important characteristic of sheet I is that it isrelatively porous and permeable as compared with the base sheet 3 inregard to the intermediate layer 2 when in softened or molten condition.When the combined sheet is subjected to heat and pressure, the illm 2will migrate, pass or strikethrough the porous sheet to provide asealing adhesive film on the surface of the porous sheet insufficientamount to form a strong seal, seam or bond at any area where desired.The porous sheet net only permits the adhesive nlm to migrate to thesurface of the sheet, but it adhesive iilm thereby preserving when thesheet is creased, folded or seamed. The

continuity of the intermediate film is thus not broken or impaired byhandling, use, .or when the sheet is converted into containers andreceptacles, or during any packaging operations', thereby tending toretain the initial vapor and moistureproof and other protectiveproperties of the combined sheet.

Such sheet material is used to form bags, receptacles, containerreceptacles, tubes and construction which are generally referred to as acontainer in the appended claims. For exdiiliculties have been suitablecomposition and of= also serves to reinforce the its continuity,

cartons, packages, linings for the like of any suitable The sheet isfolded so that the dense sheet 3 is 5 by neat sealing the sheet toitself as illustrated in Figure 6 or by use of any suitable external l0adhesive. The bottom seam 3| is then formed by applying heat andpressure to the bottom edge 'I'lle seam is shown in larger then theupper seam 3l is formed by applying heat and pressure to the area A. Asshown in superposed areas of the porous sheets are brought in facetoface relationand the 111m 2 at these zo areas is driven through to theinter faces between e contacting areas of the sheet I so as to form avery strong and tight seam.

Many other types of packages may be made form a bond at the overlappedportions to form "aseamasillustratedinliguresiland If tween theoverlapped portions instead of using heat and pressure. The ends of thesheet material are then folded over in any suitable desired folds asshown, for example, in Figure 7. Heat and pressure may then be appliedto the ends over 40 we may apply the composition only in certainpredetermined areas and of any suitablecon'tr. 'I'he composition, forexample, may be applied ln the form of bands or stripes at the marginsor other portions between the sheets so that the sheets areheat-scalable only in such areas. The adhesive composition may also beapplied by means of knurled or specially contoured rollers so as toapply the adhesive in suitably spaced application a. sumclent quantityof theadhesive is applied so that it lwill migrate through'the poroussheet to form a seal or bond.

Any suitable base Asheet material 3 is selected depending upon theparticular usage of the final product, such as paper, paper board,regenerated cellulose, glassine, parchment paper, rubber hydrochloride,cellulose acetate, ethyl cellulose, vinyl resins, any suitable syntheticresin foils, metal foils and the like. 'Ihe sheet material may betreated so as to impart any desired additional ousness to the adhesiveused, wet-strength, greaseproofness and flexibility. In the case ofpaper, it may be suitably coated and supercalendered for printingpurposes.

The sheet I is selected so as to be relatively porous as compared withthe base sheet 3, and of such structure as to permit migration of themolten or softened intermediate layer 2 to the surface of the poroussheet, through the material of the sheet itself or through anyinterstices, pores, channels, openings or perforations present in thesheet I. In other words, the sheet I is selected so as to have suitablephysical or structural characteristics so as to permit the molten orsoftened adhesive layer 2 to migrate or pass outwardly to the exposedsurface of the porous sheet. Depending upon the type of porous sheetselected, the molten adhesive will migrate either through the substanceof which the sheet may be made or through any interstices, pores,channels,

slits or openings existing in the sheet. Light weight paper tissue, forexample, has a porous structure formed by interlacing of cellulosicilbers which permits the molten or softened adhesive to pass through thesheet readily.

Our invention, however, is not restricted to the use of paper tissuesheets. We may. use any suitable type of porous, woven or reticulatedsheets, such as woven and knitted fabrics, netting, and the like. We mayalso use comparatively dense film on the outer surface of the poroussheet. The porous paper sheet may be treated if desired withurea-formaldehyde resins, or melamine resins, in small amounts, say 1 to5% by weight, to increase its wet-strength without however affecting itsporosity and other original physical characteristics. Both the basesheet and porous paper sheet may be wax-sized or dry-waxed to increasetheir waterproofness, moldproofness, wrapping machine workability, etc.

combining so as to control penetration or migration of the compositionthrough both combined sheets. The ingredients of the composition usedmay be suitably selected and compounded so as to have suitable viscosityso' as to be non-penetrating with respect to the sheets to be unitedduring the uniting operation. The conditions A under which the sheetsare combined, such as speed of uniting, temperature of application ofthe In any particular combination of base sheet..

and porous sheet the intermediate adhesive layer is of such characterthat upon application of heat and pressure to the combined sheet theintermediate layer upon melting or softening will be driven or migratedifferentially through the porous sheet and penetrate to the surfacethereof, rather than tend to migrate through the base sheet whichresists the migration of the adhesive therethrough as it is relativelymore impervious and/or dense than the porous sheet. -The adhesive, inother words, will take the path of least resistance and' will penetratethrough the porous sheet and only partially, if at all, through therelatively denser base sheet to generate an adhesive sealing film on thesurface of the porous sheet.

'I'he sheet i may be treated so as to permit migration of the adhesiveonly at certain predetermined areas. This may be accomplished, forexample, by lacquerin'g a porous paper sulphite tissue sheet in certainpredetermined areas so that the adhesive will not migrate through thesheet at such treated areas. A dense type of sheet may also be providedwith suitable openings, slits, or pinholes at certain predeterminedareas through which the adhesive. may migrate, but not elsewhere.

We find it advantageous to form the intermediate adhesive iilm so as tohave a basis weight of at least about 1% to 2 times or preferablyl morethan the basis Weight of the porous sheet when using, for example, apaper base sheet of 17 lb. sulphite and 9 lb. porous sulphite papersheet. When such thickness of the intermediate film is provided therewill be suicient adhesive composition to bond the sheets together, andalso upon application of heat and pressure, the intermediate compositionwill penetrate and saturate the porous sheet to such extent as tomigrate to the surface and form a suitable bonding illm at the outersurface thereof.

Suitable thermoplastic intermediate adhesive layers which we may use areselected or blended microcrystalline waxes; microcrystalline waxeshaving one or more added ingredients such as various elastomers, resins,gums, rubber, synthetic rubber, isobutylene and butylene polymers,

higher fatty acids as aluminum stearate, oleate or palmitate in amountsfrom 1 to 30% by weight; parailin wax containing any of the previouslymentioned ingredients added thereto and in about the same amounts;cellulose derivative compositions; synthetic resins, such asphenol-formaldehyde resins, ureaformaldehyde resins, vinyl resins;asphalts; natural gums; protein-containing compositions such as zein;and casein. These compositions are utilized for combining and adheringthe base sheet to the porous sheet in any known manner, as previouslyexplained, so as to control selectively the degree of penetration of thecomposition into the base and relatively porous sheet. When usingthermoplastic hot-melt compositions having wax as the base ingredient,we may chill the combined sheets at the point of adhesive, chilling ofthe combined sheets also can be controlled in any known .manner toprevent penetration. In this way we obtain a heatsealable sheet whichhas a continuous flexible uniform layer of the intermediate sealingcomposition without any of the composition being present on the outerexposed surfaces of the sheet. We may retain the original unimpairedphysical surface characteristics of the sheet materials used so thatthey can be printed, coated, glued or treated in any desired mannerwithout disturbing the intermediate layer which is activated andprovides a sealing means only upon application of heat and pressure toselected areas of the combinedsheet.

The following are typical specific examples of our sheet material, thenumerals preceding each component being the same as in the drawings,

weights being given per ream (480-24 x 36) CouroNrNr Example 1 Poundsweight per ream 1. Porous dry-waxed sulphite tissue paper-- 13.2

2. Microcrystalline wax M. P. 1409a160 F.-- 19.3 3. High wet strengthbleached kraft paper-- 33.5

' Total 66.0

Example 2 1. Porous sulphite tissue paper 9.0 2. 3% aluminum stearate,5% ester gum, and 92% microcrystalline wax M. P. 145 F., by wt 422.0 3.One side clay coated paper 40.0

Total.A r11.0

4 u Example 3 A1. Porous sulphite .tissue paper 9.0

2. 3% aluminum stearate, 5% ester gum, and 92% microcrystalline waxM.-P. F., by wt 20.0 3. Supercalendered sulphite paper 17.0

Total 46.0

Example 4 Total e 56.0

Example 5 Porous sulphite tissue paper- 2. 3% aluminum stearate, 5%ester gum, and 92% microcrystalline wax M. P. 145 F., by wt 25.0 3.Highly plasticized glassine 30.0

Total 64.0

' heat-sealable containers Example 6 i. Porous sulphite tissue paper 9.02. 97% by wt. microcrystalline wax M. P. 14S-7 F. and 3% by wt..aluminum stearate l-- 19.0 3. Highly hydrated greaseprooi sulphitepaper 17.0

Total 45.0

Example 7 v 1. Porous sulphite tissue paper 9.0

2. 3% aluminum stearate, 5% ester gum, and 92% microcrystalline wax M.P. 145 F., by wt 30.0 3. 0.016 in. machine calendered paper board 200.0

'rom 239.()

Our sheet materials are suitable for making and for packaging orwrapping any desired articles. Overlapped portions of the container orwrapper can be sealed by applying heat and pressure thereto aspreviously explained to form a very strong and tight seal. Inasmuch asour intermediate lm is not exposed, any materials packaged in our sheetmaterial will not come into direct contact with the sealing fllm. In theprevious types of externally coated heat-scalable sheet materials therewas a tendency for these coatings to peel and crumble,

particularly at low temperatures prevailing for packaging and storingfrozen foods, thereby contaminating the packaged foods. Our inner filmis protected against damage, puncture, abrasion, adhesion of foreignsubstances, dirt, etc. by being covered by the porous sheet. Our sheetswill not block or stick together since they` have no external coatingsto cause adhesion. Both outer sides of some of our laminated sheets maybe printed if desired. Usually only the exposed face of the base sheetis printed for packaging purposes.

Our combined sheet material acteristics which make it highly suitable asa container or wrapper for foodstuffs. It is highly moistureproof inboth flat condition as well as after folding or scoring as the adhesivelayer is supported by the porous sheet and is highly flexible, water andmoistureproof. Our composite sheet is very pliable, flexible and easilyfolded. It has a little spring-back as compared with ordinary sheetswhen folds are made during packaging operations, in both manual andautomatic packaging operations. When our sheet material is folded ittends to remain in the folded condition and does not resist bonding whenseams are formed. Thus a minimum of heat is required for forming sealsat the overlapped portions and the packaged contents are thus lesslikely to be deteriorated by the heat applied. Some materials such asyeast, for example, are very sensitive even to slight heat. Our sheetmaterials provide very eifective heat-sealable wrappers for yeast. Suchyeast packages have excellent keeping qualities and longer shelf lifethan prior packages. On account of the flexibility and continuity of ourillm our sheet material produces square and well formed packages. Nodisruption of the intermediate film will occur at the corners of thefolds when packages are made as the porous sheet serves to reinforce andprotect the intermediate film in those areas where the previous types ofexposed coatings are liable to has many "char- 8 crack and peel duringfolding and creasing operations. losing their protective qualities.

Numerous modifications and other combinations of laminated sheetmaterials may be made ut the essential features of our invention. Forexample, instead of using a single base sheet we may utilize a suitablebase sheet made of two or more plies of sheet materials selected so asto have any desired characteristics. The 4base sheet may also beprovided with a continuous thermoplastic 111m on both faces to which arelatively porous sheet is united so that such triple-ply sheet will beheat-sealable on either face.

Our sheet materials are suitable for forming heat-sealable bags,receptacles, containers, cartons. tapes, labels, tags, pouches,envelopes. tubes, gaskets, caps. bottle closures and the like. In makingbags, cartons and receptacles of any kind the base sheet can constitutethe exposed surface of the package, while the porous sheet provides theinner surface of the container which contacts the materials packagedtherein. After packaging the materials the open ends can be readilysealed by application of heat and pressure, either contacting superposedportions of the porous sheet in face to face contact or by sealingoverlapped portions in the same manner.

tion utilizing the essential and signiicant features of our invention asfully disclosed herein. It is intended to include such modificationswithin the scope of the appended claims.

We claim:

1. A laminated container having wall portions thereof formed of aheat-scalable sheet comprising in adhered condition a relatively densebase sheet material, an intercalated continuous flexible thermoplasticfilm and a thin relatively p`orous tissue sheet adhered to said film,said film not substantially penetrating said sheet materials and beingof a predetermined basis weight and confined to the inner surface of theporous sheet, the outer exposed surface of said porous sheet beingsubstantially unchanged from its original characteristics, selectedportions of said sheet being overlapped and having at least one poroustissue surface at the interfaces of the overlapped area and adheredtogether by an adhesive film generated at the interfaces of saidoverlapped portions byapplication of heat and pressure to said selectedportions and migration of said intercalated film through said poroussheet to the surface area thereof.

2. A laminated container having wall portions thereof formed of aheat-sealable sheet comprising in adhered condition a base sheetmaterial of cellulosic material having a relatively dense structure, anintercalated continuous flexible thermoplastic lm and a thin relativelyporous tissue sheet adhered to said film, said film not substantiallypenetrating said sheet materials and being of a predetermined basisweight and confined to the inner surface of the porous sheet, the outerexposed surface of said porous sheet being substantiallyunchanged fromits original 3. A laminated container having wall portions thereofformed of a heat-sealable sheet comprising in adhered condition a basesheet material of metal foil, an intercalated continuous flexiblethermoplastic film and a thin relatively porous tissue sheet adhered tosaid film, said film not substantially penetrating said sheet materialsand being of a predetermined basis weight and confined to the innersurface of the porous sheet, the outer exposed surface of said poroussheet being substantially unchanged from its original characteristics,selected `portions of said sheet being overlapped and having atleast oneporous tissue surface at the interfaces of the overlapped area andadhered together by an adhesive film generated at the interfaces of saidoverlapped portions by application of heat and pressure to said selectedportions and migration of said intercalated film through said poroussheet to the surface area thereof.

4. A laminated container having wall portions thereof formed of aheat-scalable sheet comprising in adhered condition a relatively densebase sheet material, an intercalated continuous flexible thermoplasticfilm comprising microcrystalline wax and a thin relatively porous tissuesheet adhered to said film, said film not substantially penetrating saidsheet materials and being of a predetermined basis weight and confinedto the inner surface of the porous sheet, the outer exposed surface ofsaid porous sheet being substantially unchanged from its originalcharacteristics, selected portions of said sheet being overlapped andhaving at least one porous tissue surface at the interfaces of theoverlapped area and adhered together by an adhesive film. generated atthe interfaces of said overlapped portions by application of heat andpressurelto said selected portions and migration of said intercalatedfilm through said porous sheet to the surface area thereof.

5. A laminated container having wall portions thereof formed of aheat-scalable sheet comprisingin adhered condition a relatively densebase sheet material, an intercalated continuous flexible thermoplasticfilm comprising a Wax and an elastomer and a thin relatively poroustissue sheet adhered to said film, said lm not substantially penetratingsaid sheet materials and being of a predetermined basis weight andconfined to the inner surface of the porous sheet, the outer exposedsurface of said porous sheet being substantially unchanged from itsoriginal characteristics, selected portions of said sheet beingoverlapped and having at least one porous tissue surface at theinterfaces of the overlapped area and adhered together by an adhesivefilm generated at the interfaces of said overlapped portions byapplication of heat and pressure to said selected portions and migrationof said inter- 10 calated film through said porous sheet to the saidsurface area thereof.

6. A laminated container having wall portions thereof formed of aheat-sealable sheet comprising in adhered condition a relatively densebase sheet material, an intercalated continuous flexible thermoplasticfilm comprising a wax and rubber 1 to 30% by Weight and a thinrelatively porous tissue sheet adhered to said film, said film notsubstantially penetrating said sheet materials and being of apredetermined basis weight and confined to the inner surface of theporous sheet, the outer exposed surface of said porous sheet beingsubstantially unchanged from its original characteristics, selectedportions of said sheet being overlapped and having lat least one poroustissue surface at the interfaces of the overlapped area and adheredtogether by an adhesive film generated at the interfaces of saidoverlapped portions by application of heat and pressure to said selectedportions and migration of said intercalated film through said poroussheet to the surface area thereof.

'7. In a container formed of a heat-scalable sheet material having inadhered condition a relatively impermeable base sheet material, anintercalated continuous fiexible thermoplastic film and a thinrelatively porous tissue sheet adhered to said film, said film being ofpredetermined basis weight and not substantially penetrating said sheetmaterials, and being confined tc the inner surface of the porous sheet,the outer exposed surface of said porous sheet being substantiallyunchanged from its original characteristics, a seam formed of selectedportions of said sheet material positioned in overlapped relation tobring portions of said porous sheet. in face to face contact and adheredtogether by an adhesive film generated at the interfaces of saidoverlapped portions by application of heat and pressure to said selectedportions and migration of said intercalated film through said poroussheet to the surface area thereof.

ROBERT A. FARRELL. CHARLEY L. WAGNER.

REFERENCES CITED The following references are of record in the le ofthis patent: i

UNITED STATES PATENTS Number Name Date 2,048,123 Howard July 21,19362,154,083 Bergstein Apr. 11,V 1939 2,184,139 Cunnington Dec. 19, 19392,371,314 Rhodes et al. Mar. 13, 1945 2,333,330 Moore Nov. 2, 19432,054,116 Abrams et al. Sept. 15,1936 1,937,518 Henderson et al. Dec. 5,1933

